A fiber optic faceplate is a commercially available element which is formed of, for example, glass and is further processed by grinding and polishing its opposing major surfaces. One of the two opposing surfaces of the faceplate is then attached to a device such as, for example, a CCD sensor. The device is then positioned in an optical circuit or system, and a suitably formed end of an optical fiber is contacted or attached to the second opposing major surface of the faceplate.
A first faceplate mounting technique currently in use calls for mounting a fiber optic faceplate directly onto the surface of the sensor or other device with a thin coating of optical coupling compound therebetween. The faceplate is then locked into place with an epoxy or similar resin. While this technique keeps a gap between the faceplate and the sensor to a minimum, there is a problem of mounting the faceplate without causing damage to the active area of the sensor or to the surface of the faceplate. Also, variations in the gap between the sensor and faceplate can occur where the surface of the sensor is uneven.
A second faceplate mounting technique currently in use calls for holding the fiber optic faceplate in a fixture which can monitor the image of the faceplate as the position of the faceplate is adjusted over the sensor. When the image is in a satisfactory position, the faceplate is locked into place with an epoxy or similar resin. The problem with the second faceplate mounting technique is that it is slow. It is to be understood that an optical coupling compound is used between the sensor and the faceplate in the first and second faceplate mounting techniques. This coupling compound is a gel having an index of refraction which provides desired light transmission characteristics.
The most common problem associated with mounting fiber optic faceplates to devices such as CCD sensors is poor gap control between the faceplate and the sensor or device due to variations in dimensions of the package, the sensor or device, or the faceplate. These variations in dimensions can appear from sensor to sensor, or across one sensor. In a sensor, a gap larger than, for example, 100 microns, or a non-uniform gap, affects the Contrast Transfer Function of each pixel of the sensor by allowing light to spill over into adjacent pixels. Damage to the sensor or faceplate can also result from non-uniform gaps.
It is desirable to be able to quickly and consistently make a good optical coupling between a fiber optic faceplate and a CCD sensor without causing damage to the CCD sensor.